The files were released by the National Archives under the 30-year declassification rules earlier this year.
Sikh Federation UK claimed to have found a memo within the filesreferring to the possibility of the Special Air Services (SAS) unit of the British Army being involved after "an Indian request for military assistance in the setting up of a National Guard for internal security duties" during Operation Blue Star in 1984.
"Lawyers have now written to home secretary Amber Rudd demanding an independent investigation into Britain's role in one of the darkest periods in Sikh history, after new evidence was found at the UK National Archives," a Sikh Federation UK statement said.
Former Prime Minister Indira Gandhi was assassinated by her Sikh bodyguards in an apparent revenge attack a few months after the military operation on Golden Temple in June 1984.
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Sikh Federation UK, a UK-based Sikh NGO, has accused the government of a "cover-up" and its lawyers from law firm KRW Law have now written to UK home secretary Amber Rudd demanding an "independent investigation".
But the Foreign Office has insisted the files have been merely "borrowed" following concerns raised by the group.
"The FCO [Foreign and Commonwealth Office] borrowed some of their files from 1984 that were released to the National Archives so they could read the content following concerns raised by the Sikh Federation. They will return all the files in full shortly," a UK government spokesperson said.
The 2014 report refers to an official government inquiry into the exact nature of British involvement linked to theIndian Army operation at the Golden Temple in Amritsar in June 1984.
The inquiry had been ordered by then British Prime Minister David Cameron after documents released previously under the 30-year declassification rule had implied British SAS commanders had advised the Indian government as it drew up plans for the removal of militants from Golden Temple.